Q: Some of my PNG textures can't be loaded; I get some obscure error code "12". It worked fine with the old version, though!
Sparrow now uses Apple's GLKTextureLoader class to load images. While this has several advantages (e.g. async texture loading), it has the downside that this class is a little picky when it comes to PNG images. Some image processors save your PNGs with 16 bits per pixel, and those can't be loaded. Using the command line tool "convert" (part of ImageMagick), you can easily fix those files:
convert -define png:bit-depth=8 input.png output.png
UPDATE: Sparrow 2.1 got rid of "GLKTextureLoader", because it caused a lot of problems (beside the one mentioned here). So this error shouldn't pop up any longer!